Zodiac sign

Gemini

Direct answer

Gemini is the third zodiac sign: mutable air, ruled by Mercury, associated with language, curiosity, learning, multiplicity, exchange, and quick perception.

Zodiac SignsThe Great Almanac DictionaryUpdated 2026-09-26

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At a glance

In astrology: Gemini is mutable air, ruled by Mercury, opposite Sagittarius, and often works by comparison, naming, and rapid association.
Found in: Zodiac Signs
Related: Zodiac, Sun Sign, Moon Sign, Rising Sign

Deeper Almanac guide: Gemini zodiac guide. This dictionary entry is a concise definition page; the linked guide remains the long-form topic page.

The zodiac constellation figures ranged along an engraved ecliptic — Zodiac field guide · visual guide **Gemini**
Gemini is mutable air, ruled by Mercury.
The sign glyph and elemental field orient the archetype without reducing it to a stereotype.

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What sets Gemini apart

Gemini is the mutable sign that ends spring, and the old texts call it bicorporeal, double-bodied, like Virgo, Sagittarius and Pisces. It is pictured as twins, and its constellation holds the two stars Castor and Pollux. Of the three air signs, Libra weighs and Aquarius holds a pattern, but Gemini moves between points, so its air is carried by exchange and comparison. No classical planet is exalted here; medieval Western tables placed the North Node's exaltation in Gemini. Jupiter is in detriment, opposite Sagittarius.

Sun enters: about 21 May
Quality: mutable and bicorporeal in Ptolemy's scheme
Detriment: Jupiter, from the opposite sign Sagittarius
Exaltation: none for the seven planets; the North Node in medieval Western tables
Twin stars: Castor and Pollux mark the heads of the twins

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Gemini in the traditional textbooks

Gemini is the first of the double signs and the first air sign. Its twin stars carry planetary natures in Ptolemy: Castor, which he calls Apollo, takes the nature of Mercury and Pollux, called Hercules, that of Mars. Abu Ma'shar gives the Head of the Dragon its exaltation here at 3 degrees and the Tail its fall. Dykes notes that this is Persian and Indian lore and that he has never seen it used in practice.

Ruler: Mercury. Ptolemy gives it to Mercury because it is never more than one sign from the Sun, nearest to both luminaries. Its detriment is Jupiter, the ruler of Sagittarius, the opposite sign.
Exaltation in this sign: the Head of the Dragon at 3 degrees. Fall in this sign: the Tail of the Dragon at 3 degrees.
Triplicity (air): Saturn by day, Mercury by night, Jupiter as partner (Dorotheus).
Nature (Abu Ma'shar): hot, moist, sanguine; taste sweet; masculine, diurnal; late spring, double.
Ptolemy's class: bicorporeal (mutable). On the body, its rear parts strengthen the body and its fore parts weaken it.
Body (Abu Ma'shar): chest and arms (al-Qabisi: shoulders, arms, hands).
Wind (Firmicus): the east wind.
Lands (Abu Ma'shar): Jurjan, Armenia, Azerbaijan, Gilan, Egypt, Barqa.

The bounds and decans of Gemini

The widest bound is Mars's, at 7 degrees, and the narrowest bound is Venus's, at 5 degrees. Mercury, the ruler of Gemini, holds the bound at 1 to 6 degrees.

Here are the Egyptian bounds of Gemini, counted from 0 degrees of the sign:

Mercury: 1 to 6 degrees (6 wide)
Jupiter: 7 to 12 degrees (6 wide)
Venus: 13 to 17 degrees (5 wide)
Mars: 18 to 24 degrees (7 wide)
Saturn: 25 to 30 degrees (6 wide)

Laid over the three decans of Firmicus Maternus and al-Qabisi, they fall like this:

The first decan, degrees 1 to 10, belongs to Jupiter. The bounds inside it: Mercury 1 to 6, Jupiter 7 to 10.
The second decan, degrees 11 to 20, belongs to Mars. The bounds inside it: Jupiter 11 to 12, Venus 13 to 17, Mars 18 to 20.
The third decan, degrees 21 to 30, belongs to the Sun. The bounds inside it: Mars 21 to 24, Saturn 25 to 30.

The stars of Gemini, and what the sources say it symbolizes

None of the sources we hold gives Gemini a scriptural symbol, so there is no Bible-astrology reading to report. What the texts do record is how Gemini sits in the scheme: Ptolemy counts it bicorporeal and masculine, and Firmicus puts it in the east wind with Libra and Aquarius.

Ptolemy gave the stars of Gemini these planetary natures, in the first book of the Tetrabiblos:

the feet, Mercury and some Venus
the bright stars in the thighs, Saturn
Castor ("Apollo"), Mercury
Pollux ("Hercules"), Mars

The story behind Gemini

Gemini carries twin symbolism and belongs to the mutable signs.

The spiritual meaning of Gemini

Spiritually, Gemini asks whether curiosity is serving truth or scattering attention.

Why Gemini matters

Gemini matters because it shows where a chart needs questions, variety, words, contact, and the freedom to connect one idea with another.

How to read Gemini

Astrologers reach for Gemini when interpreting communication, siblings, learning style, nervous energy, writing, trade, short movement, and the house where the chart gathers information.

Gemini in practice: an example

Gemini on the tenth house may point to public work involving teaching, writing, sales, media, translation, or many roles at once.

Where readings of Gemini go wrong

It is a mistake to reduce Gemini to inconsistency. A Gemini placement may be tracking more variables than others can see.

Sources and editorial method

This entry summarizes the tradition in the Almanac's own words; where no source is listed, it is an editorial summary rather than a primary text, and symbolic readings are named as the tradition's, not as fact.

Source: The Great Almanac Dictionary
Category: Zodiac Signs
Aliases: Gemini sign, Gemini zodiac sign
Last updated: 2026-09-26

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ZodiacThe Zodiac is the twelve-sign wheel used as astrology's core sign language. Sun SignSun Sign is the birth sign of the Sun and the most familiar doorway into astrology. Moon SignMoon Sign is the birth sign of the Moon and a key indicator of emotional patterning. Rising SignRising Sign is the sign on the eastern horizon at birth and one of the most personal chart factors. ElementElement groups the zodiac signs into fire, earth, air, and water. ModalityModality describes whether a sign initiates, stabilizes, or adapts.

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